Technologies are helping cities and neighborhoods beat the heat

Cities across the United States have found relief from high temperatures this summer with the help of technologies that protect roofs, sidewalks and other surfaces from the sun’s blazing rays.

Some of these technologies have been around for more than a decade but are seeing greater demand as global temperatures rise. For example, Washington, D.C., has built more than 3,200 green roofs covering 9 million square feet, compared with about 300,000 square feet in 2006, according to federal and city officials.

Other technologies, such as super-reflective coatings for sidewalks, streets, and windows, have become effective and affordable enough for widespread use.

Los Angeles’ Pacoima neighborhood, a densely populated location sandwiched between freeways and an industrial park, has partnered with GAF, a New Jersey-based roofing manufacturer, to coat a basketball court, a municipal park and neighborhood streets with a reflective coating.

“There is too much asphalt and a lack of investment in tree canopies,” said Melanie Paula Torres, 24, a community organizer with the group Pacoima Beautiful. “Given the fact that we are in an industrial area, this contributes to urban development.” Heat island effect.”

The reflective coating lowered air temperatures in the test area 6 feet above the ground by 3.5 degrees Fahrenheit during extreme heat days, and surface temperatures by 10 degrees, according to Jeff Terry, GAF’s vice president of corporate social responsibility and sustainability.

Hot conditions are worst in urban heat islands, which can be up to 10 degrees hotter than the surrounding suburbs, and occur when buildings, roads and other infrastructure absorb and re-emit the sun’s energy.

Cooling techniques mitigate this. Green roofs absorb heat before it can penetrate the buildings below. Super-reflective coatings reflect visible sunlight and invisible infrared rays away from surfaces to keep them cooler. An ultra-white coating developed at Purdue University promises even more protection, although the product is not yet commercially available. Each strategy helps reduce energy use.

“The important thing is to help people affordably cool their homes and workplaces,” said Jane Gilbert, chief heat officer for Miami-Dade County, which has seen a record 46 straight days with a heat index over 100 degrees this summer. The more efficient we can make buildings and air conditioning systems, the less we contribute to greenhouse gases as well as waste heat going into our urban heat islands.

Miami is one of the cities most vulnerable to the urban heat island effect, along with San Francisco, New York, Chicago and Seattle, according to an analysis by Climate Central, a New Jersey-based nonprofit that researches the effects of climate change. Its analysis found that 41 million people living in 44 cities face an urban heat island effect of at least 8 degrees. Nine US cities had at least 1 million people exposed to urban heat of 8 degrees or higher due to the local built environment.

To combat the heat, some cities are taking advantage of federal money and other incentives to convince local builders to convert office buildings to greener, cooler places.

In Miami-Dade County, officials used federal funds to outfit 1,700 public housing units with new low-energy air conditioning units. Local officials also introduced a successful amendment to Florida’s building code, which would require cool reflective roofs on all new commercial buildings starting in 2024, and enrolled 150 buildings in a voluntary energy audit program to track improvements to cut energy use and keep temperatures down.

New York, Chicago, Philadelphia, Toronto and other cities are promoting green roofs through tax credits and other incentives in an effort to lower energy bills and lower ambient temperatures, according to Stephen Beck, president of Green Roofs for Healthy Cities, a Toronto-based organization. Green Roof and Wall Industry Association. Green roofs can be 30 to 40 degrees cooler than similarly sized roofs, while reducing waste heat from air conditioning units, Beck said.

In the Pacoima neighborhood of Los Angeles, Torres says residents have told her that streets and playgrounds have gotten cooler since the reflective paint was finished in August 2022.

“The first thing that always comes up is heat waves when you look down the street. They don’t see them anymore,” Torres said.

The next step is to install reflective roofing materials on a few homes as part of a cooling effort in the neighborhood. “We want to continue to put together solutions to create an overall great community with multiple strategies,” Torres said.

Changing the urban landscape to adapt to extreme heat requires money and technical know-how, according to city leaders and academic experts. But they also acknowledge the need to keep people safe as global temperatures rise.

“Any single solution will not necessarily be able to address the entire problem, but by systematically applying solutions that work on a site-by-site basis, we can make a difference in the urban heat island effect,” said David Sailor, professor of geography. Science and Urban Planning at Arizona State University.

Write to Eric Niiler at eric.niiler@wsj.com